Free-flowing road treating material



Patented Dec. 31, 1935 UNITED STATES PATENT OFF-ICE No Drawing. Application-March -14, 1934,

Serial No. 715,510

"4 Claims.

The invention relates to the treatment'of ice- .covered road surfaces and the like, which on account of their slippery condition cause a serious traffic hazard. It particularly concerns improved materials for the treatment of such icy roads and Walks .to relieve their slippery condition, and .methods of preparing such materials.

It has been customary to strew finely divided .gritty materials-such as sand, cinders, ashes, etc., upon icy surfaces to overcome their slipperiness and make them safer for travel. For large or extensive operations, sand is ordinarily used, which under systematicv street and road maintenance is often stored in piles until required for use. Ordinary fine bank sand, such as is preferred "for use when available, will largely pass a No. standard sieve. It normally contains about 3 to 6 per cent of moisture when stored in piles, but at times due to wet weather or other .cause its water content may be even higher. The presence of the moisture tends to make the sand 'agglomerate and cake together, so that 'when'it is used for spreading on a road surface, for instance, it does not permit uniform distribution, particularly in small amounts. In practice, therefore, excessively large amounts .of such normally moist sand are usually employed for covering the icy surfaces. "The moist sand can naturally be dried prior to use, but this is not convenient 'or even practicable under usual service 36 conditions, and the provision of a suitable drier in any case would too greatly increase the ex-. pense of handling the sand. Furthermore, assuming the sand were to be dried, it would be rendered less satisfactory for the use here in question, because dry sand does not adhere to ice. If used on icy roads in cold weather, dry sand is easily displaced by passing traffic, or blown off by wind, so that it is much less effective than it should be to prevent slipping of persons or vehicles passing over the surface. In addition to which, the use of excessively large amounts of sand or like material, in an attempt to overcome the aforementioned disadvantages makes the treatment of long stretches of roadway not only too costly, but also impossible in emergencies resulting from ice storms to overcome the hazard to traffic rapidly and economically with any reasonable amountof equipment and material.

An object of the invention is to provide a simple and easy method of treating such moist sand or the like to render it free-flowing without necessity for drying the same. Another object is to cause the gritty particles of the sand to :adhere to ice and embed themselves in it quick- 1y, so asto minimize the loss of efiectiveness-due' to being blown off or being displaced by trafiic. A further object is to make it possible totreat longstretches of road rapidly and economically. To the accomplishment of the foregoing and related ends, the invention, then, consists in the method hereinafter fully described and particularly pointed out in the claims. 7

Inaccordance with my invention I mix a finely divided gritty material, normally having caking tendenciespwing to its natural water content, and a free-flowingcomminuted water-soluble dehydrating agent capable of absorbing such water. By the term water-soluble dehydrating agent is meant a-solid water-soluble salt-normally having water of crystallization that is sufficiently dehydrated to be able to 'absorbsubstantial amounts of water withoutcaking when incomminutedform. I have found that if a finely divided grittymaterial and a suitably comminuted Water-soluble dehydrating agent be mixed together in certain proportions, a freeflowing mixture results. Such mixture, since it is free-flowing, may be spread readily and. uniformly upon icy road surfaces. Since the dehydratingagent thereby associated with the gritty material is water-soluble, this causes some local melting of the iceabout each grit particle that comes .in contact. with ice. The grit particles, therefore, become anchored to or em bedded in the surface of the ice and subsequently are not dislodged readily from the road surface by the passing vehicles or wind. Since the grit particles anchor themselves to the ice, the tendency for vehicles to skid is substantially or completely overcome by the use of such mixtures. Furthermore, inasmuch as the mixture is freeflowing'and can be thinly spread, therefore, on the road surface, a very substantial saving in grit material can be had, andlong stretches of highway may be rendered safe for travel in a short time and at small expense. V

In compounding my mixture I bring together a finely divided gritty material and an amount 45 of comminuted dehydrating agent equal to from 2 to 5 or 6 times the free water content of the gritty material, and intimately mix the same so thatthe free water is substantially absorbed by the dehydrating agent and the mixture thereby 50 rendered free-flowing. Commercially available partially dehydrated calcium chloride containing from '77. to 83 percent or more of calcium chloride, the balance being water, the size of the particle of which is finer than that of the 55 gritty material is suitable for the purpose. For example, sand containing from 3 to 6 per cent of water and of such particle size that at least 80 per cent will pass through a No. 10 standard sieve may be mixed with partially dehydratedcalcium chloride, containing not more than 23 per cent of water and'comminuted so as to. pass through a No. 40 standard sieve, or preferably a No. 100 sieve, in the proportion of 100 lbs. of such sand to from 6 to 36 lbs. of such calcium chloride.

These materials may be mixed together in a rotating barrel mixer or other similar device.

It is more convenient to mix the materials while applying the mixture to a road surface with the aid of a truck driven over the road at a constant speed. On the truck two feed. hoppers may 7 be mounted, the outlets of which are led into a common screw conveyor discharging onto .a revolving horizontal spreader disk driven by a chain and sprocket attached to a wheel of the truck. The hoppers may be loaded with screened gritty material and comminuted dehydrating agent, from a supply of these carried on the truck. By regulating the rate of discharge from.

the outlets of the hoppers the materials can be proportioned and mixed by and in the screw conveyor. ture resulting may be spread uniformly and thinly upon a road surface. Such mixture may be used upon icy roads, sidewalks and the like at the rate of about 0.2 to 0.4 lbs. per square yard.

The improved distribution of ordinary bank' sand, containing from 3 to 6 per cent of water as it comes from the pits, which can be obtained when rendered free-flowing by 'my method, makes it possible to reduce the quantity of'sand used from between 5 and tons per mile to between about 1 and 2 tons per mile of road 16 feet wide. In addition to such saving, the sand adheres to the ice on the road and not only more effectively prevents skidding but also remains thereon for a much longer time. More important, is the fact that in emergencies resulting from ice storms, highways can be made safe in a very much shorter time and with less equipment than heretofore.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the method herein disclosed, provided the step stated by any of the following claims or the equivalent of such stated step be employed.

In this manner the free-flowing mix- I therefore particularly point out and distinctly claim as my invention:-

1. In a method of preparing a free-flowing gritty material for treating ice-coated roads and the like, the step which consists in intimately mixing moist sand of such particle size that at least 80 per cent thereof will pass through a No. 10 sieve and comminuted partially dehydrated calcium chloride containing not more than 23 per cent of water and of such particle size that it will pass through a No. 40 sieve, in the proportion of from 6 to 36 lbs. of such calcium chloride per 100 lbs. of such sand.

2. In a method of preparing a free-fiowing gritty material, for treating ice-coated roads and 7 a 3. In a method of preparing a free-flowing gritty material for treating ice-coated roads and the like, the step which consists in intimately mixing sand containing from 3-6 per cent of water, said sand having a particle size such that at least 80 per cent thereof will pass through a 'No. 10 sieve, and comminuted partiallydehydrated calcium chloride containing not more than 23 per cent of water, and of such particle size that it will pass through a No. 40 sieve, in the proportion of from 636 lbs. of such calcium chloride per 100 lbs. of such sand.

4. A free-flowing grit material for applying to ice coated roads and the like comprising a mixture of moistsand containing from 3 to 6 per cent of water and of such particle size that at least 80 per cent will pass through a No. 10 standard sieve and partially dehydrated calcium chloride containing not more than 23 per cent of water and of such particle size as to pass through a No. 40 standard sieve, in the proportions of 1007lbs. of such sand to from 6 to 36 lbs. of such calcium chloride.

WILLIAM R. COLLINGS. 

